(1) Field of the Invention
The present invention relates to a counterbalance apparatus for use in moving a work surface. In particular, the present invention relates to a counterbalance apparatus for vertically moving the work surface of a work station where the counterbalance apparatus exerts a constant force on the moving work surface. A counterbalance apparatus mechanically related to the current counterbalance apparatus is described in Ser. No. 08/584,266 filed on Jan. 11, 1996 which is herein incorporated by reference. A U.S. Provisional Application was filed on Dec. 31, 1997, as Ser. No. 60/070,132.
(2) Description of the Related Art
The related art has shown various systems and mechanisms for vertically adjusting work surfaces or table tops. Illustrative are U.S. Pat. No. 484,707 to Garee; U.S. Pat. No. 2,649,345 to Hubbard; U.S. Pat. No. 4,130,069 to Evans et al; U.S. Pat. No. 4,183,689 to Wiraes et al; U.S. Pat. No. 4,381,714 to Henneberg et al; U.S. Pat. No. 4,619,208 to Kurrasch; U.S. Pat. No. 4,651,652 to Wyckoff; U.S. Pat. No. 5,243,921 to Kruse et al; U.S. Pat. No. 5,322,025 to Sherman et al; U.S. Pat. No. 5,443,017 to Wacker et al and U.S. Pat. No. 5,456,191 to Hall.
In addition, U.S. Pat. Nos. 5,400,721 and 5,311,827 both to Greene show a load compensator for a spring counterweight mechanism which includes a snail cam.
U.S. Pat. No. 660,868 to Reid shows a counterbalance system for a table top which uses a chain and pulley with a weight. Similarly, U.S. Pat. No. 3,543,282 to Sautereau describes a drawing board having a counterbalance mechanism which includes pulleys and cables and which allows for easier vertical movement of the drawing board. U.S. Pat. No. 4,156,391 to Ubezio describes a counterbalance apparatus for table tops which uses a leaf spring as the means for providing the counterbalancing force. U.S. Pat. No. 4,351,245 to Laporte describes a counterweight system which uses cables and pulleys in combination with a cam mechanism.
Also, of some interest are U.S. Pat. No. 2,918,273 to Whisler et al and U.S. Pat. No. 3,582,059 to Van Ooy. Whisler et al shows a control device for a spring. Van Ooy describes a shock absorber where the wire of the compression spring is provided with one or more roller shaped guide members coaxial with the wire and rotatable about it. The guide members around the compression spring substantially eliminate wear and noise owing to sliding friction.
Only of minimal interest are U.S. Pat. No. 300,887 to Owen; U.S. Pat. No. 424,711 to Homan; U.S. Pat. No. 3,845,926 to Wahls; U.S. Pat. No. 3,885,764 to Pabreza; U.S. Pat. No. 4,415,135 to French; U.S. Pat. No. 4,625,657 to Little et al and U.S. Pat. No. 5,513,825 to Gutgsell. Owen shows an adjustable trestle for supporting scaffolding. Homan shows an extendable lamp standard. Wahls shows a seat pedestal which uses a vertically extending double telescoping tube to raise and lower the seat. The pedestal also includes a toggle linkage locking mechanism for locking the pedestal at a given height. Pabreza describes a telescoping seat pedestal which uses an elastomer block as a locking means. French describes a device for supporting a chair seat which uses a hydraulic cylinder. The hydraulic cylinder uses the flow of fluid to control the raising and lowering of the seat and the lack of fluid flow to lock the seat in place. Little et al shows a retractable keyboard support. Gutgsell shows a telescopic adjustable height apparatus having a locking means.
Also of some interest is United Kingdom Patent No. 281,884 to Coppock which shows a folding table having an adjustable height.
There remains the need for a counterbalance mechanism which allows for vertical movement of the table top or work surface at a constant rate by application of a constant force and which is easily installed into an existing table or work station.
Objects
It is therefore an object of the present invention to provide a counterbalance apparatus which allows for vertical movement of a work surface using a constant force. Further, it is an object of the present invention to provide a method for vertically moving the work surface of a work station using a constant force. Further still, it is an object of the present invention to provide a counterbalance apparatus which has a damper which prevents the work surface from exceeding a predetermined speed. Still further, it is an object of the present invention to provide a counterbalance apparatus which allows for adjustment of the initial preload on the apparatus to compensate for the change in load on the work surface without changing the amount of force needed to move the work surface. Further still, it is an object of the present invention to provide a counterbalance apparatus which is easily and quickly installed into an existing table or work station. Further, it is an object of the present invention to provide a counterbalance apparatus which is durable and inexpensive to manufacture.
These and other objects will become increasingly apparent by reference to the following drawings and the description.